The OP declines to say. He does, however say, that the treatment he has received is not on account of a protected characteristic, and he says nothing to indicate that he may have been hasty in reaching that conclusion.

The OP has asked what his options are. On the information given, I see none. If he gives some idea of the kind of thing that may have happened, there may be a different answer.

You may be able to assist him to understand the nature of the protected characteristic you are encouraging him to identify.